In the classic form of isotonic training, free weights on dumbbells or barbells are raised and lowered along a curved path about some axis. The axis itself passes through some joint of the body such as the elbow or shoulder. A deficiency of some weightlifting exercises exists in that when the weight is directly above or below the axis, very little torque is being exerted about the axis, and accordingly, at these certain positions, the muscles are exerting little effort even though the primary muscles being exercised may still be capable of exerting a strong force at these points.
An example of the type of exercise referred to above is a curling movement for the biceps muscle on the front of the upper arm. In performing a curl, as a weight is lifted from a lower position with a user's arm extended downwardly to an upper position where the arm is bent at the elbow, a moment created about the elbow is continually reduced as the weight is lifted to the upper position. Thus, substantially less bicep effort is needed to hold the weight near or in the upper position resulting in the biceps becoming unstressed almost in a rest period. Over time, any accumulated rest periods will detract from the effectiveness of the exercise so that the muscular development is impeded.
Over the years, efforts have been made to provide isokinetic devices which strive to at least maintain the level of resistance applied to a muscle over a fuller range of the exercise. One such device is disclosed in U.S. Pat. No. 4,231,569 to Rae issued Nov. 4, 1980. Rae discloses a device that is used to extend the standard bar or dumbbell weight outwardly of the user's forearm to increase the leverage produced by the weight. This device includes a triangular frame for carrying the weight, a handgrip and a forearm brace at corners of the triangle configuration. The user's forearm will come into contact with the brace only through some portions of arcuate movement of the user's arm. The weights swing freely through the remainder of arm motion with the forearm brace disengaged from the user's forearm. The effect with the weight hanging freely is no different than the effect experienced with ordinary dumbbells.
U.S. Pat. No. 4,607,840 to Harper issued Aug. 26, 1986 discloses yet another weight training apparatus in the form of a frame, a handgrip and a bar for mounting weights outward of the handgrip. First and second braces are also provided towards the rearward end of the frame and extend in opposite directions relative to the plane of the frame. These braces engage opposite sides of the user's forearm so that weight training plates can be mounted at an extended distance beyond the hands of the user in order to apply selective leverage against the user's arm. A portion of the frame is telescopically adjustable so as to vary the distance between the handgrip and an axis of the bar.
U.S. Pat. No. 4,943,052 issued Jul. 24, 1990 to Powers shows an exercising barbell provided with a rigid frame having gripping, support and weight portions spaced apart and oriented such that the center of gravity of the barbell is spaced from both the gripping and support portions. The gripping portion is suited to be gripped by an exerciser's hand, and the support portion is suited then to cooperate with a part of the exerciser's body spaced from the gripping hand. Straps for a support portion may be looped around and secured in a loop fashion to hold the support portion to the spaced part of the exerciser's body. This forms a two-point support of the barbell relative to the exerciser, to allow the exerciser to move the barbell vertically between lower and upper portions in the course of the exercise whereby the muscles of the exerciser must be stressed.
Nothing in the prior art, however, provides an exercise device which maintains resistance throughout a full range of movement while also offering a variable angular adjustment of the weights relative to a framework supported on one's forearm. In addition, there is no capability shown in the prior art for providing variable spacing between a pair of forearm braces attached to the framework.